An air bag has been quickly increasing in its installing rate in recent years as one of the safety parts for cars. The air bag is used for such a purpose that, in car collisions, a sensor perceives the shock, gas of high temperature and high pressure is generated from an inflator and the airbag is quickly developed by the gas whereby the collision of the bodies or, particularly, the heads of a driver and a passenger to steering wheel, windshield, door glass, etc. is prevented and protected. Until now, a coating woven fabric coated with synthetic rubber such as chloroprene, chlorosulfonated olefin or silicone has been used for an air bag because its heat resistance, gas blocking property (low air permeability) and flame retardancy are high. It has been also conducted to add a coloring agent to a resin composition for checking whether a coating agent is used, whether uneven application of coating agent exists, etc.
The resin including the synthetic rubber as mentioned above has been used as a coating agent after making into a solution using an organic solvent. In this regard, there is a problem that the organic solvent is vaporized so that the environment of particularly the working place is polluted. Thus, at present, use of the silicone of a solvent-free type is a mainstream. In the silicone of a solvent-free type, however, the rate of solid in a coating agent is 100% whereby there is a limitation for making the coating amount small and it has been technically difficult to apply at the rate of not more than 10 g/m2. Since the adhered amount of the resin is too much, there has been a problem for achieving an object of making an airbag light in weight and compact in size which has been demanded in recent years.
As a means for making the coating amount small without using organic solvent, a method of conducting an impregnation treatment using a water-dispersible resin has been known (e.g. see Patent Documents 1 and 2). When a resin dispersed in water as such is applied to a woven/knitted fabric, etc., a water-dispersible pigment is usually used taking the dispersibility in a solution into consideration although that is not mentioned in the Patent Documents. In this regard, there has been a problem that, when the adhered amount of the water-dispersible resin is reduced, unevenness of the water-dispersible pigment is apt to become visible. There is still another problem that, when water freshly adheres to the dry fabric, the pigment is dispersed in the water once again whereby color shading happens.
When the adhered amount of the resin is made as small as possible or, to be more specific, when it is made 8 g/cm2 or less, color shading is apt to become visible since the resin existing on the surface of base fabric becomes small. In addition, when water is present in the base fabric after drying, the pigment is apt to move and, even if it moves only a little, the color shading is prominent. As such, it has been difficult to suppress the color shading together with making the adhered amount of the resin dispersed in water small.
Patent Document 3 discloses a technique where, when a solid powder which is dispersed in water in the presence of a surfactant is used as an aqueous emulsion of silicone, the adding amount of solid powder is made within a range of 0.1 part by mass to less than 5 parts by mass. However, adhered amount of the aqueous silicone emulsion is 8 g/m2 or more and, moreover, the aqueous silicone emulsion is not self-extinguishable when its applying amount is made small whereby there is a problem that an flammability test (JIS D 1201; horizontal method) demanded for airbags for automobiles cannot be cleared. There is no disclosure therein for a technique concerning a coated fabric in which the burning rate is 80 mm/min or less or, particularly, which is self-extinguishable and in which color shading hardly happens upon adhesion of water in spite of low applying amount.
As mentioned hereinabove, when an adhered amount of a water-dispersible resin is made small, color shading is apt to becomes visible and, particularly in the case of a non-cross-linked resin suitable for recycling, the resin is sometimes re-dispersed by water even after heat-dried.